How to calculate Tank 1&2 fuel level AD_Value?

[nosrednamot]

As an example Tank 1 '0' level has an AD_value of 986 in both level flight and tail low.
How do you arrive at 986?

In my case I have a 20 gallon tank with 10 data points (2 gallon increments) - a tail dragger Murphy Rebel.
Float senders.
Is the AD_Value a resistance (ohm) reading or a calculated # like pounds of fuel * volume per gallon?

[Rob Hickman]

You put a known amount of fuel in the tank and read the AD number from the screen and use it in the table.